Scroll-type fluid compressors have a wide variety of applications. One common usage is in automotive air conditioning where a refrigerant gas is pressurized within the compressor and later evaporated to provide cooling.
Such compressors have a movable scroll member and a fixed scroll member. The movable scroll member has a scroll portion that is offset from and partially contacted with a scroll portion of the fixed scroll member so that sealed chambers are defined between the scroll members. The movable scroll is oscillated in a revolving manner under the influence of a cammed drive. Thus, as the movable scroll revolves, the sealed chambers are contracted towards the center of the scrolls so that the gases therein are compressed. In operation, refrigerant gases are introduced to a sealed chamber near the periphery of the scroll, as the scroll revolves, the sealed chamber "shifts" towards the center of the scrolls, thereby compressing the gases therein. The compressed gases are then discharged from the center region of the scrolls.
Generally, in scroll-type fluid compressors, it is considered important to assure that sliding contact portions of both the fixed and movable scrolls are sufficiently lubricated and sealed during use. For example, Japanese Laid-Open Patent Publications Nos. 59-185892 and 58-98687 disclosed prior art compressor designs.
In the former design, (Japanese Laid-Open Patent Publication No. 59-185892), an oil passage is provided in at least one of the scrolls. The oil passage communicates with an oil reservoir in the discharge chamber and has an opening at the distal surface of the spiral portion. A plurality of recesses are provided on the proximal wall of the opposing scroll. The recesses intermittently cause the oil passage to communicate with the compressing chamber at intervals synchronized with the revolutions of the movable scroll.
When the movable scroll is revolved, the oil passage and the recess intermittently allow the oil reservoir in the discharge chamber to communicate with the compressing chamber. At such times relatively large quantities of lubricating oil are transfered from the oil reservoir into the compressing chamber. This lubricating oil becomes mist and is, in an excessive amount, mixed with a refrigerant gas. When the compressed refrigerant gas is discharged into an external cooling circuit for circulation, the lubricating oil mist is also discharged into the cooling circuit and is circulated therewith. This lubricating oil tends to accumulate on the inner walls of the evaporator within the cooling circuit. The accumulated oils tend to reduce the amount of heat exchange in the evaporator, thereby reducing its efficiency.
In the latter design, (Japanese Laid-Open Patent Publication No. 58-98687), spiral shaped sealing members are provided along the distal surfaces of spiral portions of both the fixed and movable scrolls. These sealing members contact and slide across the proximal wall surface of the opposing scroll. A passage for pressure fluid is provided in at least one of the scrolls. The passage carries a pressurized fluid within the sealing member against the proximal wall of the opposing scroll.
Pressurized fluid is delivered to a recess in the distal surface of the scroll. The pressurized fluid is used to press the sealing member against the opposing wall in order to maintain a good fluid seal. A discharge passage is then provided to reduce the pressure of the pressurizing fluid at selected time.
Several sources are contemplated for the pressurizing fluid. The primary embodiment contemplates using the compressed refrigerant taken from a high pressure region between the scrolls. Alternatively, an external source may be used. It is also suggested that lubricating oil can be used as the pressurizing fluid. However, the described construction is unduly complicated since it requires periodic activation of a piston to reduce the pressurizing fluid pressure and when external supply sources are provided, a relatively complicated delivery structure would be required.
In the latter described design, when lubricating oil is used for a pressure fluid for pressing the seal member, a lot of lubricating oil is introduced into the compressing chamber via a fluid leading passage at revolutions of the movable scroll as well as the former. Accordingly, there is also the same problem that this lubricating oil is attached to the inner wall or the like of the evaporator in the cooling circuit and prevents heat exchange.